1. Field of the Invention
The present invention relates generally to single chain Fv fragments of tumor-associated antigen binding antibodies. The invention further relates to single chain Fv conjugate molecules and their use in the delivery of biologically active molecules to cancer cells as well as in directing T cells to respond to tumor-associated antigen expressing cancer cells.
2. Background Information
Microarray analyses have revealed that there are genes expressed by CLL cells that are not expressed in other lymphoid tissues. Coupled with the observation that CLL cells also express a highly restricted immunoglobulin repertoire, cells likely express distinctive antigens that also could be targeted for immunotherapy. Conceivably, chronic lymphocytic leukemia (CLL) cells in particular also might have such leukemia-associated antigens (LAA).
However, CLL patients typically develop hypogammmaglobulinemia and worsening immune deficiency, which impairs their immune response to LAA-targeted vaccines. Implicated in the abnormal immune function are immune-suppressive factors and an acquired functional deficiency of CD154. Furthermore, CLL cells are particularly poor at antigen presentation, which appears in part secondary to inadequate leukemia-cell expression of immune co-stimulatory/adhesion molecules.
Indeed, despite the presence of tumor-associated antigens (TAAs) like LAAs expressed in different cancers, cancer patients typically are unable to mount an effective immune response against existing or developing tumors. TAA binding antibodies have been used to develop potential cancer vaccines with mixed degrees of success. Many such TAAs represent developmental or differentiation antigens that have restricted expression. Fc containing antibodies to TAAs are often cleared relatively quickly from circulation and may be recognized only by one type of MHC molecule, limiting their usefulness in therapy.
Activation of CLL cells via CD40-ligation can reverse its immune-suppressive phenotype. Furthermore, CLL cells transduced with an adenovirus encoding the ligand for CD40 (Ad-CD154) can function as more effective antigen-presenting cells (APCs). In addition, they can effect ligation of CD40 on bystander leukemia B cells and stimulate autologous leukemia-reactive T cells both in vitro and in vivo. However, targeting of CD154 modified T cells to CLL cells remains to be achieved.
Tyrosine kinases are important mediators of the signaling cascade, determining key roles in diverse biological processes like growth, differentiation, metabolism and apoptosis in response to external and internal stimuli. Studies have implicated the role of tyrosine kinases in the pathophysiology of cancer. Schlessinger J. (2000) Cell, 103:211-225; and Robinson et al. (2000) Oncogene, 19:5548-5557, MacKeigan and colleagues used a large-scale RNAi approach to identify kinases that might regulate survival and apoptosis of a human tumor cell line (HeLa), RNAi to ROR1 was found as one of the most potent in inducing apoptosis among the set of RNAi targeting each of 73 different kinase-encoding genes. MacKeigan et al. (2005) Nat Cell Biol., 7:591-600. However, these investigators did not examine the expression or function of ROR1 protein in these cells.
ROR1 is a membrane-receptor with an intracellular kinase-like domain and extracellular Frizzled-like cysteine-rich domain, which is common to receptors of members of the Writ-family. ROR1 is member of the ROR family that is evolutionarily conserved among Caenorhavditis elegans, Drosophila, mice and humans. Wilson C, Goberdhan D C, Steller H. Dror, a potential neurotrophic receptor gene, encodes a Drosophila homolog of the vertebrate Ror family of Trk-related receptor tyrosine kinases. Proc Natl Acad Sci USA, 1993; 90:7109-7113; Oishi et al. (1997) J Biol. Chem., 272:11916-11923; Masiakowski et al. (1992) J Biol. Chem., 267:26181-26190; Forrester et al. (2002) Cell Mol Life Sci., 59:83-96; and Oishi et al. (1999) Genes Cells, 4:41-56. In rodents, ROR1 is expressed primarily in developing cephalic neural crest in the dorsal part of the diencephalons and mid-hind brain boundary during embryogenesis. In most species examined, expression of ROR1 apparently attenuates during embryonic development, becoming negligible at term. ROR1 mRNA was reported to express in infant brain, renal cancer and colon cancer. In a recent study, it was found that ROR1, at both mRNA and protein level, was highly expressed in CLL B cells but not normal B cells. Moreover, it was found that ROR1 is a receptor for Wnt5a, which could induce activation of NF-κB when co-expressed with ROR1 in HEK293 cells and enhance survival of CLL cells in vitro. Another study found that ROR1 was expressed in acute lymphocytic leukemia (ALL) as well. Shabani et al. (2007) Tumour Biol., 28:318-326; and Baskar et al. (2008) Clin Cancer Res., 14:396-404.
Expression of full-length ROR1 in numerous cancer cell lines and samples, but not other tissues, including blood or splenic lymphocytes of non-leukemic patients or normal adult donors, and also generated mouse anti-sera against full-length human ROR1. Fukuda et al., Blood: ASH Annual Meeting Abstracts 2004 104, Abstract 772 (2004) (incorporated herein by reference in its entirety). The polypeptide and coding sequences for ROR1 have been reported elsewhere and are also incorporated herein by this reference (see, e.g., Accession Nos. NP—005003.2 and NM—005012). Surprisingly, it has also been discovered that cancer cells which express the Wnt5a protein, such as CLL cells, not only bind ROR1 but have a survival advantage conferred as a consequence.
Thus, ROR1 is an embryonic protein that is expressed uniquely on certain cancer cells, including in CLL, small lymphocytic lymphoma, marginal cell B-Cell lymphoma, Burkett's Lymphoma, and other cancers (e.g., breast cancers), but not on normal adult tissues and cells. It is therefore a potential TAA target for modulation of an immune response to ROR1 expressing cancer cells (“ROR1 cancers”).
Yet, as noted, patients with CLL typically develop disease-related hypogammaglobulinemia and respond poorly to vaccines. The progressive acquired immune deficiency associated with CLL accounts for much of the morbidity related to this disease. However, as shown previously, following treatment with autologous Ad-CD154-transduced CLL cells, most patients had increased serum IgM and IgG and developed a specific antibody response against adenovirus and some developed anti-CLL autoantibodies. Although virus infections occasionally can induce autoantibodies, autoantibodies were not detected against other blood cells or human CD154. Likewise, there were no increases in the titer of antibodies to a recall antigen, tentanus toxoid, except in one patient who was immunized with tetanus toxoid following the second infusion of autologous Ad-CD154-CLL cells. Therefore, CLL patients could respond well against other vaccines administered during the course of such treatment, potentially allowing for generation of protective immunity against infectious agents that commonly afflict patients with this disease. The invention provides such a vaccine, as well as targeting means for drug delivery to ROR1 cancer cells.